Generally a braiding machine can have spools with thread, yarn or wire mounted upon a rotor which is driven about a common axis, namely, an axis of rotation of the rotor by a main drive via a transmission. As a consequence of the rotation of the rotor, the elements from the spools are entrained about the axis or are wound on a flexible core to form the braid, some of the spools being movable in the opposite direction and, via an appropriate mechanism, these yarns, threads or wires are brought under or over the elements from other spools to form the braid.
The result is a flexible product, namely, the braid which is withdrawn from the machine by an extracting or withdrawal drive which can have a disk over which the elongated flexible product is carried out of the machine and, if desired, wound up.
The withdrawal speed of the elongated product must be exactly matched to the speed of the aforementioned rotor so that the yarns will have the desired orientation and pitch in the product and, in general, product quality will not vary over the length thereof.
It is generally known to provide a device for withdrawing flexible elongated product from such machines by providing a control frequency which is determined by the speed of the main drive operating the withdrawal drive with this frequency or a frequency or signal derived from the control signal, and to control the latter frequency or the parameter.
In such systems, the speed of the withdrawal drive can be influenced or dependent upon the speed of the main drive. The influence upon the speed of the withdrawal drive is based upon the control frequency generated by the main drive and which, in turn, can be influenced in its origin since it permits the desired proportionality between the withdrawal speed and the main drive speed which affects the quality and character of the flexible product. Should the main drive speed increase, the withdrawal speed drive speed will increase in the fixed proportion and should the main drive speed diminish, the speed of the withdrawal drive will diminish in the fixed proportion. The pitch of the yarn, threads or wires in the braid will thus remain constant over the entire manufacturing process and the quality of the product will not fluctuate with variations in speed.
An unregulated asynchronous motor can be used for the main drive since its speed variations are always translated into proportional variations in the speed of the withdrawal drive. The coupling between the two drives, although electronic, thus merely replaces the fixed ratio mechanism transmissions between the main drive and withdrawal drive which previously were used.
In the withdrawal of a flexible product from a fabricating machine, care must be taken to avoid the development of flaws in the product which may result from a defect in fabrication. For example, it is conceivable that a thread breakage will occur. In such a case, the particular thread is no longer withdrawn but can be wound up in an unbraided fashion resulting in a thickening in the product. The thickening can result in a hang-up of the product to a greater or lesser extent and thus to greater defects in the product, overloading of the withdrawal drive, the development of excessive tension in the product, etc. For this reason in conventional braiding machines in the transmission system between the main drive and the withdrawal drive shearing pins or toothed shearing wheels of plastic can be provided for automatic mechanical interruption of the link between the fabricating machine to the withdrawal device when such difficulties occur, thereby preventing damage to the rotor, overloading of the withdrawal drive, etc.
If the withdrawal drive is not mechanically coupled to the main drive but is connected thereto via an electrical path with a servodrive, such overloading conditions can be compensated electronically.
The electrical systems used heretofore, however, are complex and expensive and the regulatory devices necessary to prevent overloading are also expensive to provide and operate and may not always be reliable.